1. Field of Invention
This invention relates to an automotive clutch and, in particular, to an improved clutch cover assembly useful in such a clutch.
2. Brief Statement of the Prior Art
The automotive clutches most commonly used by automotive manufacturers (OEM) incorporate a conical spring diaphragm for developing the pressure which is imparted to the pressure plate of the clutch assembly. The pressure plate frictionally engages with the clutch plate and slippage, if any, in the clutch assembly occurs between these members. The conical spring diaphragm typicaly used in automotive clutch applications is a modified Belleville spring in which a number of radial slots are cut in a conical spring member to permit flexing of the member when the clutch is disengaged and engaged and when the release bearing is forced against the conical spring diaphragm.
The conical spring diaphragm is mounted in the pressure plate subassembly in a position to exert an axial force on the pressure plate in its extended conical position and to release the pressure when flattened by the force applied by the release bearing during disengagement of the clutch.
The conical spring diaphragm is generally not suitable for use in high speed application since the pressure it exerts on the pressure plate is constant, independent of engine speed. Since this spring member must be provided with a tension that is sufficiently low to permit ease of disengagement of the clutch through the clutch pedal of the vehicle, the maximum pressure it can exert on the pressure plate is limited. This force is often inadequate for high speed applications and slipping occurs in the clutch. For this reason, specially designed clutches which utilize lever arms and compression springs have been used for racing applications. Centrifugal weights have been attached to these lever arms such that the centrifugal force developed by rotation of the pressure plate subassembly is applied to augment the force of the compression springs on the pressure plate. Centrifugal weights, however, have not been successfully used with diaphragm springs.
Another failing of the conical spring diaphragm, which can occur during ordinary use of the vehicle, is caused by over centering of the diaphragm which locks the clutch in a disengaged position. The over centering occurs when the conical spring member is moved past its flat or center position and resiliently moves to a reversed position with the clutch permanently disengaged, requiring dismantling of the clutch to restore the diaphragm to its proper position.